John Edwards (1); (1) Process NMR Associates, Danbury, CT, U.S.A.
1H nuclear magnetic resonance spectroscopy (NMR) has been used by chemists for 50 years as the ultimate tool for molecular structure elucidation. Another area where NMR spectroscopy excels is the quantitative analysis of complex mixtures where multiple individual molecular components produce NMR signals that can be identified and quantified to produce a chemical fingerprint that is useful for i) evaluating incoming raw materials; ii) following mash, sour mash, and sparging chemistry; iii) following the progress of fermentations; iv) following the appearance of undesirable components; and v) observing the chemistry changes during barrel and bottle aging processes. In a single NMR spectrum it is possible to observe in one experiment, in 175 µL of sample, with little to no sample preparation, a wide range of chemical components such as alcohols (ethanol, methanol, 1-propanol, isobutanol, iospentanol), organic acids (lactic, acetic, pyruvic, succinic, citric, malic, tartaric), esters (ethyl acetate and ethyl lactate), amino acids (alanine, GABA, valine, proline, arginine, tryptophan, phenylalanine, tyrosine, histamine), and detailed residual malt and carbohydrate chemistry (glucose, fructose, sucrose, lactose, alpha(1-4)- and alpha(1-6)-glucans, and more) as well as adjunct components from additions of coffee or cocoa (caffeine and theobromine). The chemical fingerprint is extremely detailed and allows brewers to determine what is happening within their brew from the mash to the bottle. The NMR technique, though excellent for providing detailed information down to a few ppm of the various components does not observe hop chemistry present in the finished beers, as the concentration is below the limit of detection of the analysis. The technique is particularly useful for following sour beer processes.
John Edwards received a B.S. degree in chemistry from Durham University in Durham, U.K., in 1986 and then a Ph.D. degree in physical chemistry from the University of South Carolina in Columbia, SC, in 1990, specializing in NMR spectroscopy. He spent seven years working for Texaco Research running the NMR facility and then started his own analytical NMR service and consulting business, where he utilizes NMR to support several hundred industrial and academic customers. For the past 18 years he has developed quantitative approaches for the analysis of pure materials, as well as complex mixtures such as beer, wine, cider, and herbal supplements. He is currently collaborating with several breweries on developing a deeper understanding of where detailed chemical fingerprint information can assist brewers in their brewing process and in their quest to produce consistent products.